fix(sdk): reuse Channel in NetworkClient

[ctian1]

• Reuses gRPC Channel in NetworkClient to improve performance

[github-actions]

Test	Old	New	Diff
k256_test_recover_pubkey_infinity	124534	124534	0.0000 %
curve25519_dalek_test_decompressed_expected_value	16150463	16301602	0.9358 %
keccack_test_expected_digest_lte_100	2036984	2035584	-0.0687 %
sha_test_sha3_expected_digest_lte_100_times	1668974	1668829	-0.0087 %
sha_test_sha2_v0_9_9_expected_digest_lte_100_times	1487373	1490364	0.2011 %
curve25519_dalek_test_add_then_multiply	8806620	6412858	-27.1814 %
bls12_381_tests_test_sqrt_fp_100	980080	1110338	13.2905 %
bls12_381_tests_test_inverse_fp_100	1375050	1375050	0.0000 %
bn_test_bn_test_fq_sqrt_100	763356	763356	0.0000 %
curve25519_dalek_ng_test_decompressed_noncanonical	206954	206954	0.0000 %
rustcrypto_bigint_test_bigint_mul_add_residue	2253569	2253569	0.0000 %
bls12_381_tests_test_sqrt_fp2_100	1883164	1806718	-4.0594 %
p256_test_verify_rand_lte_100	24852154	24858841	0.0269 %
bls12_381_tests_test_inverse_fp2_100	3083020	3083020	0.0000 %
curve25519_dalek_test_zero_mul	197103	197103	0.0000 %
curve25519_dalek_ng_test_zero_mul	197063	197063	0.0000 %
curve25519_dalek_ng_test_add_then_multiply	6709078	7965073	18.7208 %
p256_test_recover_high_hash_high_recid	3283264	3405941	3.7364 %
curve25519_dalek_test_zero_msm	213024	213024	0.0000 %
bn_test_bn_test_fq_inverse_100	766356	766356	0.0000 %
k256_test_verify_rand_lte_100	24870573	24796300	-0.2986 %
rustcrypto_bigint_test_bigint_mul_mod_special	2315020	2315020	0.0000 %
p256_test_recover_pubkey_infinity	143003	143003	0.0000 %
secp256k1_program_test_verify_rand_lte_100	46747972	46830223	0.1759 %
bn_test_bn_test_fr_inverse_100	796856	796856	0.0000 %
bn_test_bn_test_g1_double_100	648027	648027	0.0000 %
bn_test_bn_test_g1_add_100	846324	846324	0.0000 %
curve25519_dalek_ng_test_zero_msm	216592	216592	0.0000 %
k256_test_recover_rand_lte_100	5599019	5617285	0.3262 %
k256_test_schnorr_verify	7029517	7028295	-0.0174 %
secp256k1_program_test_recover_rand_lte_100	6596180	6602878	0.1015 %
bls12_381_tests_test_bls_double_100	9218745	9218745	0.0000 %
rust_crypto_rsa_test_pkcs_verify_100	101950323	101832698	-0.1154 %
bls12_381_tests_test_bls_add_100	15763438	15763438	0.0000 %
secp256k1_program_test_verify_v0_30_0_rand_lte_100	46784366	46844421	0.1284 %
p256_test_recover_rand_lte_100	7264672	7264303	-0.0051 %
k256_test_recover_high_hash_high_recid	2416613	2545082	5.3161 %
secp256k1_program_test_recover_v0_30_0_rand_lte_100	6646045	6638905	-0.1074 %
sha_test_sha2_v0_10_8_expected_digest_lte_100_times	1730817	1734688	0.2237 %
sha_test_sha2_v0_10_6_expected_digest_lte_100_times	1728443	1733302	0.2811 %
curve25519_dalek_test_ed25519_verify	32349990	32349749	-0.0007 %
curve25519_dalek_test_decompressed_noncanonical	9169	9169	0.0000 %